The present invention relates to a method for informing motor vehicle drivers, digitally encoded traffic messages being received and buffered.
The Radio Data System (RDS) makes it possible to transmit supplemental and inaudible digital data in a data channel concurrently with broadcast programs. Specifications for the Radio Data System for FM radio broadcasting have been established in the printed publication Tech. 3244-E, March 1984 of the European Broadcasting Union (EBU) and elsewhere. Broadcast receivers with suitable RDS decoders can receive and decode transmitted data in addition to audio reception with the same receiver component. Thirty-two groups of 104 bits each are provided for the data transmission, each of the assigned groups being assigned to a specific service. Group 8a is presently provided for the transmission of digitally coded messages, traffic messages in particular.
The configuration and the encoding of such traffic messages are established in CEN ENV 12313-1 which is based on the proposed standard ALERT C, November 1990, published by RDS ATT ALERT Consortium. The essential elements of a traffic message are the location of the event and the event itself. This information is cataloged, i.e, a unique code is assigned to every traffic-relevant location and every traffic-relevant event. The chaining of the locations in a location database along existing roads reproduces the course. Aside from the customary equipment of a receiver with an RDS decoder, devices for decoding, storage, further processing and output of the traffic messages are required for utilization of the TMC (Traffic Message Channel).
Digitally coded traffic messagesxe2x80x94also referred to hereinafter as TMC messages for the sake of simplicityxe2x80x94can be transmitted not only with the aid of the Radio Data System but rather also, for example, within Digital Audio Broadcasting (DAB), the FI Channel (Fast Information Channel) in particular. Moreover, transmission of the messages is provided via mobile radio telephone networks, for which the broadcast channel and the SMS channel (SMSxe2x80x94Short Message Service) are suitable. In this regard, a Global Automotive Telematic Standard (GATS) is being developed at the present time. This is a packet-oriented data channel which can be operated concurrently with voice transmission via telephone. While all TMC messages must be transmitted in sequence in broadcasting systems, i.e., in unidirectional networks, transmission on request is possible with bidirectional networks.
Each TMC message is stored in memory in the particular receiver and it stays there until it loses its validity. This is implicitly the case after a quarter of an hour (after half an hour with transmission via GSM). For greater time spans, the validity time is included explicitly in the transmission, for example, xe2x80x9ctwo more hours.xe2x80x9d If an impediment lasts longer than was assumed at the beginning, the same message is sent again before it loses its validity (update message).
Traffic jams are normally reported with an extent in kilometers. However, the driver is frequently more interested in information about how much longer the traffic jam or other traffic impediment will last. When deciding whether to take a detour, which is normally more complex than the direct route, the expected duration of a traffic jam is one important consideration.
An object of the present invention is to provide the driver with information concerning the development of a traffic jam or of a different impediment based on the received TMC messages.
This objective is attained according to the present invention in that a time stamp is stored in memory with each of the received traffic messages, a measure of the duration of the event and/or the change of the extent is derived from the extents and the time stamps of several stored traffic messages relating to the same event, and the change is displayed. Although other obstructions developing over time may also be the object of the method of the present invention, it is preferably provided that the extent is the length of a traffic jam.
Various time stamps as such can be provided for the method according to the present invention which, for example, start at a time t=0 when the first traffic congestion message relating to an event is received. In the method according to the present invention, however, it is altogether advantageous if the time stamp is the particular clock time.
The change can be displayed optically or audibly, both a general trend display as well as a more precise display, for example, in kilometers per unit of time, being possible.
For example, the method according to the present invention makes clear the significance of the announcement of a traffic jam of perhaps only 5 kilometers in length but which has already been present in memory for several hours and in which the length of the traffic jam has possibly even been increased through an update message (which arrives at the same position in the TMC memory). This traffic jam is very stubborn and is worth circumventing. Also other messages such as road closings can be evaluated in a more practical manner in comparison to the mere statement xe2x80x9croad closed.xe2x80x9d
To avoid overwriting earlier time stamps, one advantageous embodiment provides that subsequent messages relating to the same event are given the time stamp of the first message relating to that event.
In navigation devices with automatic route search, a resistance value is assigned to the individual roads. In the method according to the present invention, the time duration information as well as the change of the extent are suitable for use as a resistance value for a route search.